1. Field
This disclosure relates to generating and receiving traffic for testing a network or network device.
2. Description of the Related Art
In many types of communications networks, each message to be sent is divided into portions of fixed or variable length. Each portion may be referred to as a packet, a frame, a cell, a datagram, a data unit, or other unit of information, all of which are referred to herein as packets.
Each packet contains a portion of an original message, commonly called the payload of the packet. The payload of a packet may contain data, or may contain voice or video information. The payload of a packet may also contain network management and control information. In addition, each packet contains identification and routing information, commonly called a packet header. The packets are sent individually over the network through multiple switches or nodes. The packets are reassembled into the message at a final destination using the information contained in the packet headers, before the message is delivered to a target device or end user. At the receiving end, the reassembled message is passed to the end user in a format compatible with the user's equipment.
Communications networks that transmit messages as packets are called packet switched networks. Packet switched networks commonly contain a mesh of transmission paths which intersect at hubs or nodes. At least some of the nodes may include a switching device or router that receives packets arriving at the node and retransmits the packets along appropriate outgoing paths. Packet switched networks are governed by a layered structure of industry-standard protocols.
In order to test a packet switched network or a device included in a packet switched communications network, test traffic comprising a large number of packets may be generated, transmitted into the network at one or more ports, and received at different ports. In this context, the term “port” refers to a communications connection between the network and the equipment used to test the network. The received test traffic may be analyzed to measure the performance of the network. Each port connected to the network may be both a source of test traffic and a destination for test traffic. Each port may emulate a plurality of logical source or destination addresses. The number of ports and the communications paths that connect the ports to the network are typically fixed for the duration of a test session. The internal structure of the network may change during a test session, for example due to failure of a communications path or hardware device.
Each packet in the test traffic may be a unicast packet intended for reception at a specific destination port or a multicast packet, which may be intended for reception at two or more destination ports. However, packets may be misdirected by the network. A misdirected packet may be received at one or more ports that are not intended destinations.
A series of packets originating from a single port and having a specific type of packet and a specific rate will be referred to herein as a “stream.” A source port may support multiple outgoing streams simultaneously and concurrently, for example to accommodate multiple packet types, rates, or destinations. “Simultaneously” means “at exactly the same time.” “Concurrently” means “within the same time.”
For the purpose of reporting network traffic data, the packets within a stream may be organized into flows, where a “flow” is any plurality of packets for which network traffic statistics are accumulated and reported. The packets in a given flow may be distinguished by a flow identifier contained in each packet. The flow identifier may be, for example, a dedicated identifier field, an address, a port number, a tag, or some other field or combination of fields within each data unit.
A plurality of concurrent streams may be combined to form the output from a source port, which will be referred to herein as “test traffic”. The streams within the test traffic may be transmitted sequentially or concurrently through interleaving. The interleaving may be balanced, unbalanced, and distributed among the represented streams. To test a modern “triple play” network and network equipment, the test traffic may contain simulated data, audio, and video streams.
Throughout this description, elements appearing in block diagrams are assigned three-digit reference designators, where the most significant digit is the figure number and the two least significant digits are specific to the element. An element that is not described in conjunction with a block diagram may be presumed to have the same characteristics and function as a previously-described element having a reference designator with the same least significant digits.
In block diagrams, arrow-terminated lines may indicate data paths rather than signals. Each data path may be multiple bits in width. For example, each data path may consist of 4, 8, 16, 32, 64, or more parallel connections.